MP4.2+6.0

The rear roof ones dump in the back fender area as I recall; not sure where front ones are. On my A6 they emerged near the front door hinge area I think.

Meanwhile, clear the ones in your pic. out of course. Some have nipped off those ends you have pictured, which conceptually are meant to stay kind of closed if water comes in from below (traversing streams or floods...?). But of course crap can hangs up there where it is crimped in that cross fashion.

MP4.2+6.0

That is separately possible, though rare. If it had antifreeze taste, then yes the heater core(s). But, it can also be clogged drains from the HVAC system, which would not have any antifreeze taste. Those drains are around the console area, but would be more likely to act up in humid conditions and probably wouldn't tie to winter rains. Unless that is, the plenum area is either flooded out and/or the HVAC air filter cover under the hood and below the center of the windshield is missing or pretty badly out of position.

MP4.2+6.0

originating from sunroof corners. The front ones are visible right in the rounded corners past the pop up air deflector. Not sure of the rear set up since it is buried.

As an editorial, sincere and frank comment, per the top of board sticky, this really is a classic scenario where the need for a good manual is coming out. You are unsure of what the issue is, where the drains are, etc. I personally have never had an issue since I leave roof closed anywhere near clear weather leaves, and I clear the plenum pretty regularly. Others have some reasonable ideas, but the advice is varied. Hence, a good manual. The manual covers the various drains (sunroof, plenum set up and HVAC core), and I think there are some TSBs about it. Bentley includes TSB's as part of its CD/DVD. Alldata does too, but I find theirs somewhat harder to read than the Bentley formatted ones.

To clean sunroof drains (covered in manual/elsewhere IIRC) you need a flexible tool conceptually like a multi foot long ginormous pipe cleaner. Something like a flexible plastic fiber with a safely blunt end. What you really do NOT want to do is go in there with something sharp or that could snag and could cut the drain tubes. Thus, something like the larger diameters of weed whacker nylon line are in the zone. And, you do not ever want to use high pressure air like out of a compressor driven air nozzle. If you damage those hoses or blow them loose it is a nightmare to get at them to repair what will then be a sure and permanent leak thereafter.

Panelhead

I could hear water sloshing around inside evaporator core area. Both drains were plugged.
Used small aircompressor with basketball needle to blow out. But I live south of Houston, 100% humidity most of the year. AC was running yesterday. This is 11 months a year air conditioning climate.
I have only owned the car a little over a year, 11K miles. But the AC drains dropped the inside humidity.

CWTech

It almost not HVAC related. Definitely not antifreeze inside the car.

We had heavy rains the night before and it's the first time I've had this issue.

aTOMic

My experience: water pools in the trough around the sunroof and then as we leave our (downhill) driveway (turning left), the passenger gets a lapful! I told my wife it's obvious the car dislikes her!
What gets me is that despite the millions in water ingress compensation beginning in 1998 AFAIK that the same stupid design continues to be chosen! With four drain tubes a car which is parked level should never have a pool of water as long as at least one is not clogged!
Why are there sealing nipples at the end of each which inevitably catch the silt that causes this? And the icing on this cake of fecal matter is (at least on the '04) the nipples are not easily accessible! /rant off

I read (pretty sure it was a TSB on Bentley or an SSP) that the normal sunroof "seal" allows water to enter intentionally - it is not meant to seal, that's why it's made of the mousefur-like stuff. The gasket should be replaced if worn to provide proper filtration. Only $300 + labor at the dealer. When I unclogged mine it was just a small amount of silt causing the clog- I guess the cooking measure would be a "pinch" - definitely not 1/4 tsp.. I cut the nipples off (ouch) leaving a ~4mm opening.
I bought my'98 Passat new and a few years later received a "campaign circular" for the dealer to do exactly that, so I did it myself (on that car the discharge in the door jambs, and they are huge compared to the A8's). One was already clogged
Lastly. I think one of my rear drains (on the A8) is detached, evidenced by wet headliner and dripping from the end of the trim onto rear passenger's hip. Pretty sure caused by too much air pressure trying to clear it (by previous mechanic). my advice is to access the drains, each of which is annoyingly located behind fenderliners, and cut the nipples off, then attach your wet-vac (mine just hung there by its own suction) and go into the car to be sure it's open (you'll hear it from 3 feet away); if not plenty of liquid plumr should fix it (kidding, but I'd flush with water with the vac on). Worked for me.
BTW, The rear drains are not where shown in Bentley, they're at the top of the rear inner fender (makes it extra-fun cause the tire must come off) Oh, that Art! Such a card!

haggisuk

In the year of ownership of the 8 I have cleaned the sunroof drains three times, first time was pretty much after buying it because of Internet horror stories and then evenly over the remaining time period.

On all the occasions the drains at the front of the sunroof were blocked.

Now my car does not live under trees or in the desert but I have noticed every time I have went to clean the drains there has been a build up of fine sediment in the channel around the sunroof. So my theory is this. A fine layer of dust is building up on the car and through the process of rain or natural settlement it is gathering in the valley where the sunroof seal meets the roof panel, now I usually power wash the car when I can be bothered and I think the fine dust is get forced through the seal into the channel below the sunroof that feeds the drains.

Due to the design of the terminations of the sunroof drains the fine sediment is gathering at that point due to water carrying it down at a slow rate and because of the slow rate it's not getting flushed out of the drains.

Now if my theory is correct or not is of little importance, the fact remains that my drains have been blocked every time I have checked and cleaned them.

I check my drains by parking on level ground and having the sunroof open then slowly filling the channel around the sunroof with water to see if it drains, it should drain away straight away, if it hangs around then you have blocked drains.

I tried the flexible rod solutions and failed, so not wanting to pierce the drain tubes I rigged up a bug spray bottle with a piece of hose that fitted snugly in the drain hose and sealed, I then pumped it up and squirted pressure into the drain hose on each front corner until it cleared I then proceeded to flush both corners with the bug spray bottle filled with warm soapy water to make sure they are clear.

As for the scuttle drains I usually get the Hoover with a long snake like attachment and suck out all the leaves and crap from the scuttle area then run a few kettles of boiling water through and usually find the hot water softens the debris and the rubber of the drains enough to clear them out,

I have never done the a/c drains but it is on my to do list.

I do feel the main culprits of wet interiors would be the sunroof and scuttle drains more than the a/c drains.

MP4.2+6.0

First, if the air cleaner cover isn't on top of the HVAC filter area, that is a sure fire way for water to go into the interior if the bottom drains aren't open or car is parked on slopes. Was a famous mess on the C5 A6 with a different filter set up. There the filter was barely under the edge of the windshield base with no separate cover and if plenum cover was slightly loose water went in through rear heater vents into the passenger side carpet.

Besides HVAC air cover dislodged or missing scenario, if lower heater drains are clogged--where condensation needs to get out anyway from A/C function, it will back up if water gets in or condenses there. Again, in the rain context if the plenum area is swimming in water and/or the HVAC filter cover is dislodged, same answer.

Pulling plenum cover takes less than 60 seconds to look in there generally. No brainer to check. 5 minutes to reinstall once you know the drill.

Still more likely sunroof drains in the described context, but also not just a good idea but a mandatory to keep plenum area cleaned out.

CWTech

Where the hell is a scuttle drain?

I made sure that the cabin filter and plastic were all in place, which they were. Although the sunroof drain area looks fine, perhaps it is blocked. Will try a spraybottle as suggested.

CWTech

I have found that the passenger side front sunroof drain is completely clogged. I'm on tempting to unclog it using lead to weed trimmer line. This is a pain in the ***.